1. Field of the Invention
The present invention relates to resinous polyols which are particularly useful in high solids coating compositions. More specifically, the present invention relates to resinous polyols comprising high solids polyurethane polyols which are prepared by reacting low molecular weight polyols with polyisocyanates, wherein the reaction product is characterized by the presence of a significant amount of unreacted starting polyols.
2. Brief Description of the Prior Art
In preparing resinous polyols, particularly low molecular weight ones, the full implications of using a large excess of starting low molecular weight simple polyols such as glycols had not been appreciated in the art. Certainly, the significance of using a large excess of starting polyols generally, followed by removing the attendant unreacted starting polyols from reaction products had not been appreciated in the art. Specifically, it had not been appreciated that by removing unreacted starting polyols, performance properties of coating compositions comprising the resultant resinous polyol could be affected significantly.
In the prior art preparation of low molecular weight resinous polyols, there are employed controlled amounts of starting polyols. The amounts of starting polyols are controlled in such a manner as would produce resinous polyols containing tolerable amounts of unreacted starting polyols. Usually, the unreacted starting polyols in these amounts, i.e., up to about 5 percent, are not intentionally removed from the reaction product.
In preparing art-known low molecular weight polyurethane polyols, commonly, "oligomeric polyols" such as polyester polyols are reacted with isocyanates. Generally, these reactions do not entail removal of unreacted starting polyols.
In the present invention, simple polyols can be employed in relatively large excess with the intent of substantially increasing the low molecular weight and the narrow molecular weight distribution of the resultant resinous polyols. While the reaction is attended by a significant amount of unreacted polyol, a portion or all of the unreacted polyol can be subsequently removed from the reaction product. Thus, the narrow molecular weight distribution of the resinous polyol is optimized.